Shortening Stabilization Time Using Pressurized Air Flow in Manufacturing Mesophase Pitch-Based Carbon Fiber

Abstract

Oxidation–stabilization using pressurized air flows of 0.5 and 1.0 MPa could successfully shorten the total stabilization time to less than 60 min for manufacturing mesophase pitch-based carbon fibers without deteriorating mechanical performance. Notably, the carbonized fiber heat-treated at 1000 °C for 30 min, which was oxidative–stabilized at 260 °C without soaking time with a heating rate of 2.0 °C/min using 100 mL/min of pressurized air flow of 0.5 MPa (total stabilization time: 55 min), showed excellent tensile strength and Young′s modulus of 3.4 and 177 GPa, respectively, which were higher than those of carbonized fiber oxidation–stabilized at 270 °C without soaking time with a heating rate of 0.5 °C/min using 100 mL/min of atmospheric air flow (total stabilization time: 300 min). Activation energies for oxidation reactions in stabilization using pressurized air flows were much lower than those of oxidation reactions using atmospheric air flow because of the higher oxidation diffusion from the outer surface into the center part of pitch fibers for the use of the pressurized air flows of 0.5 and 1.0 MPa than the atmospheric one. The higher oxygen diffusivities resulted in a more homogeneous distribution of oxygen weight uptake across the transverse section of mesophase pitch fibers, and allowed the improvement of the mechanical properties.

Oxidative stabilization of pitch‐polyacrylonitrile composite nanofibers electrospun by incorporating high‐percentage inexpensive pitch

“…The morphology and dispersion degree of 50% NP‐PAN carbon nanofibers as shown in Figure 10a are obviously improved in comparison with that of preoxidized sample at ambient pressure (Figure 9a), which indicates that pressurization can accelerate the oxidative stabilization of composite nanofibers and thus shorten the oxidation time. This feasible pressure of 0.08 MPa is lower than that pressure (0.1–1.0 MPa) reported in Reference 39. Although the NP‐PAN composite nanofibers with a higher content (e.g., 80% and 110%) are not completely preoxidized at the same temperature for a short duration (3 h) as shown in Figure 10b,c, the oxidation time can be greatly shortened compared with those of at ambient‐pressure preoxidation presented in Figure 9 (12–24 h).…”

Influence of Oxygen Uptake on Pitch Carbon Fiber

“…This could potentially increase mechanical properties and eliminate the formation of an under‐oxidized fiber core as indicated by other work with atmospheric pressure. [ 12 ]…”

“…This could potentially increase mechanical properties and eliminate the formation of an under-oxidized fiber core as indicated by other work with atmospheric pressure. [12] Table 1 presents the results of the fitting parameters to the EDS oxygen profiles, the oxygen weight at the center (ox c ) and edge (ox edge ), the average oxygen weight content from EDS, the average oxidation weight from the TGA experiments, and the percent difference between these oxidation percentages. The difference between the average oxygen percentage from TGA and EDS are compared.…”

“…Atmospheric pressure and composition are usually employed in the interest of keeping costs low, but the oxygen partial pressure can be altered to accelerate this process. [12] A wide variety of alternative stabilization techniques have been employed to improve the oxidation process such as plasma stabilization, sulfuric acid stabilization, nitric acid stabilization, and KMNO 4 stabilization of PAN. [13][14][15][16][17] The goal of these investigations is either to increase CF mechanical properties, reduce production cost, or investigate scientific phenomena.…”

Investigation on promotion effect of oxidative stabilization for pitch‐based fiber by co‐carbonization of coal tar pitch and atmospheric residual

“…Zhang et al studied the oxidative stabilization mechanism of CTP by free‐radical induced method, which concluded that the oxidation reaction was synergistic promoted by tremendous free radicals generated from thermolabile covalent bonds of 2,3‐dimethyl‐2,3‐diphenylbutane and reaction of pitch molecules with oxygen 13 . The oxidative stabilization time of manufacturing mesophase pitch‐based carbon fiber was successfully shortened to less than 60 min by using pressurized air flow, revealing that the higher oxygen diffusivities decreased activation energy for the oxidative stabilization and contributed to a more homogeneous oxygen distribution across transverse section of pitch fiber 20 . Furthermore, some methods, such as modifiers (Br 2 , I 2 , and S), oxidant types (H 2 O 2 , HNO 3 , and H 2 SO 4 ), and irradiation treatment (ultraviolet, plasma, and electron beam), had been performed to improve oxidative stabilization efficiency of pitch fiber 21–27 .…”